A buddy of mine just cut the muffler off of his 06 Chevy 1500 5.8 and had straight pipe welded in its place. It sounds decent, and the best part is his gas millage went from 15.2 to 21.5 miles per gallon! So has anyone done this to their Jeep? What does it sound like? Have you seen any gas mileage gains? Or any opinions?

Ehh I wouldnt reccomend it, my buddy did it on his silverado and theres a constant drone, cops will bust bawls due to "pollution" and noise or whatever. Besides, straight pipe = no back pressure = major performance decrease. a lot of NHRA cars have some sort of muffler just so theres no performance decrease.

I know its not stated here , but the OP is from South Florida, where there are no emissions, no inspections to speak of, and the cops have real policework to do instead of picking on someone for running no muffler.

Having run no muffler at one point (in between exhaust setups on my WJ), I would not recommend it, as the downpipes are not balanced at all, leading to a very cluttered sound below 2k. You need some sort of muffler to cancel out some of that. Not to mention it is extremely loud. There is a valid reason why Chrysler uses 30" long mufflers on the 4.7.

I am not familiar with how the WK Y pipe is set up, but I would bet modifying that to be equal length (or close enough), re routing the single pipe in 3" to a straight through muffler would make the sound alot cleaner, meaner, and attain the gas mileage you seek.

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eh to me the grand cherokee is supposed to be a luxury suv... running no muffler makes it sound like a trail rig... you want a throaty sound, not a garbled redneck sound(again my opinion). I just think the 4.7 and the hemi sound like crap with no muffler to balance out the note/tone

I have NO MUFFLER and two resonators on my 4.7 and NO ONE has ever told me it sounded like crap. There is no drone and it sounds mean! Adding a muffler in place of the stock is just a waste of $$$$ IMO. Cut that stock suitcase out and add a small resonator at the tip.